The best existing solutions for predistortion of power amplifiers with memory effects are predistortion methods that use polynomials or piecewise polynomials with delays. In these existing solutions, the predistortion is accomplished by the use of polynomials or piecewise polynomials with some delay terms. The disadvantages of these solutions often include one or more of the following: a non-uniform approach to handling memory effects, an ad hoc arrangement of polynomials (or piecewise polynomials) with delays, no clear metric for judging why one ad hoc arrangement is better than another, each ad hoc arrangement used ignores certain aspects of the memory effects (e.g., ignores certain cross-term effects), the predistortion is limited to the use of polynomials or piecewise polynomials, and polynomials/piecewise polynomials become unstable when a high degree is used, although orthogonal polynomial may alleviate the instability. Therefore, new solutions for predistortion that are able to address some of these known issues in are desirable.
Specific embodiments of the present invention are disclosed below with reference to FIGS. 1-11. Both the description and the illustrations have been drafted with the intent to enhance understanding. For example, the dimensions of some of the figure elements may be exaggerated relative to other elements, and well-known elements that are beneficial or even necessary to a commercially successful implementation may not be depicted so that a less obstructed and a more clear presentation of embodiments may be achieved. In addition, although the logic flow diagrams above are described and shown with reference to specific steps performed in a specific order, some of these steps may be omitted or some of these steps may be combined, sub-divided, or reordered without departing from the scope of the claims. Thus, unless specifically indicated, the order and grouping of steps is not a limitation of other embodiments that may lie within the scope of the claims.
Simplicity and clarity in both illustration and description are sought to effectively enable a person of skill in the art to make, use, and best practice the present invention in view of what is already known in the art. One of skill in the art will appreciate that various modifications and changes may be made to the specific embodiments described below without departing from the spirit and scope of the present invention. Thus, the specification and drawings are to be regarded as illustrative and exemplary rather than restrictive or all-encompassing, and all such modifications to the specific embodiments described below are intended to be included within the scope of the present invention.